why is it if you guys don't know the answer or if you don't want to answer a question do you guys leave it unanswered. At least you could do is comment back and say you don't know it to at least let people know that you have seen their questions.
There are a number of tutors who volunteer to answer questions and who are in various time zones/countries. Consquently there may not be always be a specialist available for some questions.
The easiest way for us to spot an unanswered question is a single posting, if there is a response we usually assume that the question is answered. Hence if there is a response of 'can't answer this' then it will be assumed that the question has been answered, which was not what was intended.